Square tube



FIG. 1 is an isometric view of the square tube;

FIG. 2 is an end view of the square tube of FIG. 1, the opposing end view being identical thereto; and,

FIG. 3 is a front view of the square tube of FIG. 1, the rear, top and bottom views being identical thereto.

The square tube is shown with a symbolic break in its length. The appearance of any portion of the square tube between the break lines forms no part of the claimed design. 

CLAIM The ornamental design for a square tube, as shown and described. 